1. Field of the Invention
The present invention relates to a following distance control device that controls a vehicle to regulate a distance to a preceding vehicle to a target following distance, and also relates to a following distance control method.
2. Description of the Related Art
A following distance control device executes various vehicle controls (throttle control, brake control, etc.) to regulate a distance to a preceding vehicle to a target following distance so that a subject vehicle travels at a speed relative to the preceding vehicle. In devices disclosed in Japanese Patent Application Publications No. 2004-216964 (JP-A-2004-216964) and No. 2004-216965 (JP-A-2004-216965), following distance control is cancelled when a driver starts brake operation or accelerator operation during the following distance control, and is resumed when the driver stops the above operation. Specifically, in these devices, when the following distance control is resumed, an actual following distance at the moment is used as the target following distance for the following distance control. Meanwhile, a device disclosed in Japanese Patent Application Publication No. 2004-306690 (JP-A-2004-306690) changes the target following distance when detecting the driver's intension to reduce or increase the following distance from accelerator operation or brake operation by the driver during the following distance control. For example, the driver's intension to reduce the following distance is detected from the accelerator operation with which the acceleration once reaches or exceeds the given acceleration and then is reduced. The driver's intension to increase the following distance is detected from the brake operation with which the deceleration exceeds given deceleration and from the subsequent accelerator operation to increase the acceleration.
However, during the following distance control, the driver may execute the brake operation or the accelerator operation that is irrespective of the following distance control for the purpose of the rapid deceleration to secure a safe following distance when a vehicle cuts in or for the purpose of the rapid acceleration for overtaking. In the above cases, if the target following distance is changed after the brake operation or the accelerator operation as by the devices disclosed in JP-A-2004-216964 and JP-A-2004-216965, the target following distance is changed to the one that is unintended by the driver. In addition, in the above cases, if the accelerator operation or the brake operation that exceeds the specified amount of acceleration or deceleration is detected as the driver's intention to change the following distance as by the device disclosed in JP-A-2004-306690, the target following distance is changed to the one that is unintended by the driver. Consequently, the driver may be disturbed by a need to change the following distance again to the originally intended following distance, for example.